Actually, the talk about it taking over a space is not something I have seen. I've had plants for three years and they stay in the 2' wide space I started with. A caveat - we mow the grass on both sides weekly.
As far as increasing or decreasing the "heat" level, it depends on how long you soak the ground HR in vinegar. Two minutes will make it on the hot side of mild, three minutes will mean a warm hot.
A generally accepted rule is to let the plants grow for two seasons before harvesting, then harvest after a hard freeze or even when the ground thaws in the spring. When I tried harvesting some the first year, I got enough to make about a tablespoon of HR. I tried to dig up a root very early this spring, and I could have used a backhoe. Didn't get close to getting all of it but just the main part, without all the side shoots (most of which I replanted) was 1.5 times the size of a softball! More than enough HR to last me a year!